Archivio Journal of Plant Pathology

Abstract:

Atriplex nummularia Lindl. is used in phytoremediation of saline soils in Brazil. In May 2014, plants with shoot blight were collected in Serra Talhada, Pernambuco state, Brazil. Fragments of surface sterilized symptomatic tissue were plated on potato dextrose agar (PDA) amended with 0.5 g/l streptomycin sulfate. After 5 days at 25°C in the dark, grayish white mycelial growth appeared, without formation of pycnidia after 3 weeks. A pathogenicity test with one isolate (Atn3) was conducted on 10 asymptomatic superficially sterilized green shoots of A. nummularia (20 cm length, ca. 1 cm diameter). Shoots were wounded at the center using a sterilized scalpel. Mycelial plugs (0.5 mm diameter) from the margin of actively growing colonies (PDA) were placed in the wounds and covered with parafilm, with non-colonized PDA plugs used as control. After 15 days at 25°C, all inoculated branches showed superficial blackened lesions, from which the pathogen was re-isolated. No symptoms were observed in the controls. To identify the isolate, the ITS region and the EF1-α gene were sequenced using ITS1/ITS4 (White et al., 1991), and EF1-728F and EF1-986R primers (Carbone and Kohn, 1999). The sequences showed 98% identity with the ex-type of Diaporthe inconspicua (CBS 133813) for the ITS region (KC343123) and 99% for the EF1-α gene (KC343849). Sequences of Atn3 were deposited in GenBank under accession Nos. KM816789 (ITS) and KY288068 (EF1-α). D. inconspicua was first described by Gomes et al. (2013) in Maytenus ilicifolia and Spondias mombin in Brazil. This is the first report of this fungus causing shoot blight in A. nummularia in Brazil.